Divide Array Into Equal Pairs

Problem Description

You are given an integer array nums consisting of 2 * n integers. You need to divide nums into n pairs such that each element belongs to exactly one pair and the elements present in a pair are equal. Return true if nums can be divided into n pairs, otherwise return false.

Key Insights

• The total number of elements in the array is always even (2 * n).
• For the array to be divided into pairs of equal elements, each unique element must appear an even number of times.
• A frequency count of each element can be used to determine if the pairing is possible.

Space and Time Complexity

Time Complexity: O(n)
Space Complexity: O(k) where k is the number of unique elements in the array.

Solution

To solve this problem, we can use a hash table (or dictionary) to count the frequency of each element in the array. After populating the frequency count, we check if every element has an even count. If all elements have even counts, then it is possible to pair them; otherwise, it is not.

1. Traverse the array and create a frequency map (hash table) for all elements.
2. Iterate through the frequency map and check if all counts are even.
3. If all counts are even, return true; otherwise, return false.

Code Solutions